This invention generally relates to intravascular catheters, particularly catheters for use in percutaneous transluminal coronary angioplasty (PCTA) or for the delivery of stents.
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient's coronary anatomy where the balloon of the dilatation catheter is properly positioned within the stenosis to be dilated. The balloon is then inflated with radiopaque liquid at relatively high pressures (generally 4-12 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient's coronary anatomy to dilate additional stenoses.
In addition to the dilation of stenoses, balloon catheters similar to those described above are used to deploy stents within a patient's body lumen after a dilatation has been completed or simultaneously with the dilatation in order to maintain lumen patency. In this case an expandable stent is disposed about the exterior of the balloon on the distal extremity of the catheter and the catheter is then advanced within the patient's body lumen until the stent mounted on the exterior of the balloon is at the location in which the stent is to be deployed, e.g. usually at the stenotic site of a previous dilatation. The balloon is inflated so as to expand the stent against the wall defining the body lumen and then the balloon is deflated and the catheter withdrawn from the patient's body lumen.
Advances in the development of balloon catheters for both dilatation and stent deployment have made the selection of materials difficult because of conflicting requirements. For example, higher dilation pressures has made the sealed bonding of the balloon the catheter shaft a greater requirement, but the materials from which the high pressure balloons are made, e.g. polyethylene terephthalate, polyamide (e.g. nylon) and the like, have limited the materials to which the balloon can be bonded, and thus, the materials from which the catheter shaft can be made, particularly the distal extremity of the catheter shaft where the balloon is located.
If the distal tip of an intravascular catheter is to have non-traumatic characteristics to minimize damage when passing through a body lumen, additional material limitations come into play because typical non-traumatic tips are formed from short tubular members made of relatively soft polymeric material which are secured by adhesive or fusion bonding to the distal tip of the tubular distal extremity of the catheter.
Other complicating factors in the selection of materials for intraluminal catheters is the usual requirement that the proximal shaft be much longer and much less flexible than the distal shaft section so that the proximal shaft section provides the push to the catheter and so that the more flexible distal shaft section can be readily advanced through tortuous anatomy.
The difficulties in material selection and the more complicated construction of the more recently developed catheters make their manufacture more difficult and more expensive. What has been needed is a catheter structure which simplifies the material selection and reduces the cost of manufacture. The present invention satisfies these and other needs.